Sunscreens are products combining several ingredients that help prevent the sun’s ultraviolet (UV) radiation from reaching the skin. Two types of ultraviolet radiation, UVA and UVB, damage the skin and increase your risk of skin cancer. Sunscreens vary in their ability to protect against UVA and UVB.

Ultraviolet (UV) radiation is part of the electromagnetic (light) spectrum that reaches the earth from the sun. It has wavelengths shorter than visible light, making it invisible to the naked eye. Ultraviolet A (UVA) is the longer wave UV ray that causes lasting skin damage, skin aging, and can cause skin cancer. Ultraviolet B (UVB) is the shorter wave UV ray that causes sunburns, skin damage, and can cause skin cancer.

SPF – or Sun Protection Factor – is a measure of a sunscreen’s ability to prevent UVB from damaging the skin. Here’s how it works: If it takes 20 minutes for your unprotected skin to start turning red, using an SPF 15 sunscreen theoretically prevents reddening 15 times longer – about five hours. Most sunscreens with an SPF of 15 or higher do an excellent job of protecting against UVB. Of course, SPF 50 is recommended for the best protection and prevents reddening 50 times longer.

Broad-spectrum sunscreens protect the skin from both UVA and UVB rays. The final regulations, which became effective June 18, 2012, established a standard test for over-the-counter (sold without a prescription) sunscreen products labeled as “Broad Spectrum.”

Products that pass the broad spectrum test will provide protection against both ultraviolet B radiation (UVB) and ultraviolet A radiation (UVA). Sunburn is primarily caused by UVB. Both UVB and UVA can cause sunburn, skin cancer, and premature skin aging. A certain percentage of a broad spectrum product’s total protection is against UVA.

(Alta Med Facts recommends you look for words “Broad Spectrum” and a SPF of at least 30, preferably 50.)